Field of the Invention
The invention relates generally to systems and methods for hanging tubulars from a wellhead into a wellbore. More particularly, the invention relates to a tubular hanger that is run and secured in the wellhead in a single trip without rotation.
Background of the Technology
Conventionally, wells in oil and gas fields are built up by establishing a wellhead housing at the surface and, with a drilling blow out preventer (BOP) adapter valve installed, drilling down to produce the borehole while successively installing concentric casing strings. The casing strings are cemented at their lower ends and sealed with mechanical seal assemblies at their upper ends. In order to prepare the cased well for production, a production tubing string is run into the cased borehole through the BOP, and a tubing hanger coupled to its upper end is landed in the wellhead. Thereafter the drilling BOP is removed and replaced by a Christmas tree having one or more production bores containing valves and extending vertically to respective lateral production fluid outlet ports in the wall of the tree.
In general, a tubing hanger is installed by a hanger running tool that lowers the hanger down the production bore of the wellhead until it lands on a stop shoulder. The stop shoulder is formed by a decreased inner diameter portion in a spool defining a section of the production bore of the wellhead. The shoulder provides a permanent means to stop the lowering of the tubing hanger, thereby locating the hanger within the wellhead.
One conventional method for retaining a hanger in a wellhead, often referred to as the tiedown screw method, requires drilling a plurality of bores through the wellhead spool. The bores extend radially through the spool to the production bore and are circumferentially spaced apart about the spool. A pin is inserted into each bore and extends partially into the production bore. Together, the plurality of pins define a reduced diameter shoulder in the production bore upon which the hanger is subsequently seated and/or retained. However, due to the multiple penetrations into the pressurized production bore, this approach may lead to undesirable leaks.
Other conventional methods for retaining a hanger in a wellhead often require two trips into the production bore of the wellhead—a first trip to land the hanger in the spool, and a second trip to lock the hanger in position within the spool. This approach presents some risks, especially during snubbing operations in which the hanger is positioned in the wellhead while the well still is under pressure (i.e., not killed). In particular, prior to locking the hanger in position, the hanger is subjected to the wellbore pressures, which presents the potential for well control issues. Moreover, many conventional two trip methods require rotation of the hanger to land and/or lock the hanger in position. However, rotation of the hanger subjected to wellbore pressures can be difficult and hazardous.
Accordingly, there remains a need in the art for apparatus, systems, and methods for landing and retaining a tubing hanger within a wellhead. Such apparatus, systems, and methods would be particularly well received if they did not require penetration of the spool and enabled a single-trip approach without rotation to both land and lock the tubing hanger within the spool.